A workpiece in the context of this application may comprise a mask on which a circuit pattern is to be inscribed or may be a wafer or a substrate of the actual material on which the microcircuit or device is to be formed. Since the devices and microcircuits under consideration are typically very small in size, such workpieces must be positioned very accurately and must be capable of being moved extremely precisely.
To assist in this a workpiece or a worktable on which the workpiece is mounted has been provided with a set of registration marks which are used inter alia for alignment of the system. However the presence of registration marks on the surface of a workpiece on which a device or microcircuit is to be inscribed restricts the area on that surface which can be used for this purpose. To this end circuit designers are forced to design the circuits so as to avoid the places where the marks are to be positioned.
It is thus an object of the present invention to provide an apparatus for inscribing and a method of alignment of such apparatus which allow more freedom to the circuit designer and allow greater positional accuracy to be obtained in use.